1-Propene, 2-methyl-

Formula: C₄H₈
Molecular weight: 56.1063
IUPAC Standard InChI: InChI=1S/C4H8/c1-4(2)3/h1H2,2-3H3
IUPAC Standard InChIKey: VQTUBCCKSQIDNK-UHFFFAOYSA-N
CAS Registry Number: 115-11-7
Chemical structure:
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Other names: Propene, 2-methyl-; γ-Butylene; Isobutene; Isobutylene; Isopropylidenemethylene; 1,1-Dimethylethylene; 2-Methyl-1-propene; 2-Methylpropene; iso-C4H8; Methylpropene; UN 1055; 1,1-Dimethylethene; 2-Methylpropylene
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Gas phase thermochemistry data

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Data compiled as indicated in comments:
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
GT - Glushko Thermocenter, Russian Academy of Sciences, Moscow

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	-4.29 ± 0.26	kcal/mol	Cm	Prosen, Maron, et al., 1951	ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_gas	-645.19 ± 0.25	kcal/mol	Cm	Prosen, Maron, et al., 1951	Corresponding Δ_fHº_gas = -4.27 kcal/mol (simple calculation by NIST; no Washburn corrections); ALS
Δ_cH°_gas	-650.6	kcal/mol	Ccb	Guinchant, 1918	Corresponding Δ_fHº_gas = 1.1 kcal/mol (simple calculation by NIST; no Washburn corrections); ALS
Quantity	Value	Units	Method	Reference	Comment
S°_gas	70.170	cal/mol*K	N/A	Stull D.R., 1969	This value was obtained on the basis of calorimetric data [ Todd S.S., 1936]. Experimental value of S(298 K)=288.7 J/mol*K [ Todd S.S., 1936] could not be recommended because of its large uncertainty.; GT

Constant pressure heat capacity of gas

C_p,gas (cal/mol*K)	Temperature (K)	Reference	Comment
8.528	50.	Thermodynamics Research Center, 1997	p=1 bar. Recommended values are in close agreement with other statistically calculated values [ Kilpatrick J.E., 1946] as well as with ab initio value of S(298.15 K)=293.37 J/mol*K [ East A.L.L., 1997].; GT
10.98	100.
13.58	150.
16.09	200.
19.77	273.15
21.05	298.15
21.15	300.
26.240	400.
30.915	500.
35.010	600.
38.564	700.
41.659	800.
44.357	900.
46.714	1000.
48.764	1100.
50.550	1200.
52.101	1300.
53.454	1400.
54.632	1500.
56.977	1750.
58.678	2000.
59.940	2250.
60.894	2500.
61.623	2750.
62.189	3000.

Constant pressure heat capacity of gas

C_p,gas (cal/mol*K)	Temperature (K)	Reference	Comment
18.13 ± 0.091	239.15	Scott R.B., 1945	GT
19.81 ± 0.098	272.15
21.91 ± 0.11	312.15
23.96 ± 0.12	353.15

References

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Prosen, Maron, et al., 1951
Prosen, E.J.; Maron, F.W.; Rossini, F.D., Heats of combustion, formation, and insomerization of ten C₄ hydrocarbons, J. Res. NBS, 1951, 46, 106-112. [all data]

Guinchant, 1918
Guinchant, M.J., Etude sur la fonction acide dans les derives metheniques et methiniques, Ann. Chem., 1918, 10, 30-84. [all data]

Stull D.R., 1969
Stull D.R., Jr., The Chemical Thermodynamics of Organic Compounds. Wiley, New York, 1969. [all data]

Todd S.S., 1936
Todd S.S., Thermal data on organic compounds. XV. Some heat capacity, entropy and free energy data for the isomeric butenes, J. Am. Chem. Soc., 1936, 58, 134-137. [all data]

Thermodynamics Research Center, 1997
Thermodynamics Research Center, Selected Values of Properties of Chemical Compounds., Thermodynamics Research Center, Texas A&M University, College Station, Texas, 1997. [all data]

Kilpatrick J.E., 1946
Kilpatrick J.E., Heat content, free energy function, entropy, and heat capacity of ethylene, propylene, and the four butenes to 1500 K, J. Res. Nat. Bur. Stand, 1946, 37, 163-171. [all data]

East A.L.L., 1997
East A.L.L., Ab initio statistical thermodynamical models for the computation of third-law entropies, J. Chem. Phys., 1997, 106, 6655-6674. [all data]

Scott R.B., 1945
Scott R.B., Specific heats of gaseous 1,3-butadiene, isobutene, styrene, and ethylbenzene, J. Res. Nat. Bur. Stand., 1945, 34, 243-254. [all data]

Notes

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Symbols used in this document:

C_p,gas	Constant pressure heat capacity of gas
S°_gas	Entropy of gas at standard conditions
Δ_cH°_gas	Enthalpy of combustion of gas at standard conditions
Δ_fH°_gas	Enthalpy of formation of gas at standard conditions

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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